Directional aerials



Jan. 12, 196@ s, Z|SLER 2,921,311

DIRECTIONAL AERIALS Filed Oct. 9, 1957 U ted ate mfi fO The present invention relates to improvements in dire'c-' tional aerials of the type including a plurality of elementary radiating units distributed in a uniform manner in a common plane and a reflector.

It is an object of the invention to improve the aerials of this type and'this is mainly achieved by reducing by' one half the number of the elementary :units and positioning the elementary radiating units at the 'apices of square or rectangular checker-work meshes at a distance from one another equal to about one wave-length, the directional properties of the conventional systems being thus preserved. The size of the reflector is only slightly greater than that of the aerial network, and it is provided with lateral flanges perpendicular to the plane thereof along at least a portion of its periphery, said flanges having a width of about one-half wave-length.

The invention will be best understood from the following description taken in connection with the appended drawing wherein:

Fig. 1 shows in perspective view an aerial according to the invention, and

Fig. 2 shows another embodiment of the invention.

The aerial shown in Fig. 1 includes four horizontal lines of radiating-elements, each line being constituted by eight of such elements.

The aerial is illustrated in perspective view. Radiating elements, such as R, R, R", S and T, are positioned at the apices of the angular meshes of a checker-work. Two adjacent elements such as R and R, on a same horizontal line are spaced according to the invention by one wave length, the spacing of the two adjacent elements in a vertical alignment or row, such as R and R", being also equal approximately to one wave length. At the center C of the aerial, a coordinate system comprises: a coordinate axis CN normal to the plane of the aerial, a horizontal axis CX, lying in the plane of the aerial and a vertical axis CY. Any direction of radiation may be defined by its projections CA on the plane CNX and by its projection CB on the plane CNY and thus by the angle between vectors CA and CX and the angle between the directions CB and CY.

Each of the radiating elements may be constituted for example by a dipole, a folded dipole or a Yagi array.

It will be noted that the invention is independent of the structure of the elementary aerials and is consequently applicable to aerials built from any type of elementary aerials.

It is a well known fact that the cross-section through a horizontal plane of the main lobe of the radiating diagram is determined chiefly by the spacing between the extreme rows, i.e. in the present case, by the spacing between the extreme elements R and S of the horizontal line, while the shape of the cross-section of the main lobe through a vertical plane is defined by the spacing between the extreme lines, i.e. between the extreme elements R and T of a vertical row. The presence of intermediate elements in the lines and rows has for its Paten ed Jan.- 12,1960.

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. object to reduce as much as possible the importance of D being the distance between two successive the secondary lobes.

In/the case where all the lines and all the rows are identical, the radiating diagram may be expressed as well known in the art by the combination of three elementary diagrams, to wit:

The diagram of an elementary aerial;

The diagram of a line; The diagram of a row.

If .all the elements of a. given line or row are fed in a similar manner, the diagram of a line or a row is given by the formula:

sin NU N sin N being'the number of radiating elements contained in. the line or row and U having for its value expressed as an electric angle elements of the line or the row and V being the angle 0 or the angle defined hereinabove.

In the aerials of the type described, the radiating diagram of each elementary radiator plays only a comparatively limited part since the directional properties obtained are due almost only to the summation of the effects produced by the different elementary systems. The above equation shows that G is at a maximum when sin U is minimum i.e. for values of sin V g sin V equal to 0, 1r, 211-, etc.

-In order to obtain a single main lobe, according to my invention, the secondary lobes are suppressed by using a suitably shaped plane reflector.

A reflector of infinite dimensions would eliminate the secondary lobe corresponding to D value equal to 21r since this lobe is in a direction perpendicular to the axis of the aerial, i.e. in a direction contained in the plane of the reflector.

The invention achieves the same result with a reflector Q having an area only slightly larger than that covered by the aerial network, the reflector being provided with flat flanges E, F, G, H, perpendicular to the reflector.

The flanges are preferably constituted by panels or gratings and they play a double part:

(a) In so far as the suppression of the secondary lobes is concerned, the reflector incorporating them in equivalent to a plane reflector the dimensions of which are much larger than those of the aerial network.

(b) They suppress the direct radiation of the extreme aerial elements 'in undesired directions.

Fig. 2 is a sectional view of an aerial according to the invention, wherein the radiating elements, symbolized -by parts such as R, R' and S, are spaced by one wave length from each other. The radiating elements R, R and S, have their bases positioned in a predetermined plane, and the predetermined plane containing their respective bases being spaced from reflector G by about one quarter of a wave length.

Reflector Q, as shown in Fig. 1, extends beyond the extreme aerial elements R and S by about one quarter of a wave length, in the same way as in Fig. 2.

Reflector Q also includes inturned flanges E and F which are perpendicular to the body of the reflector and extend over by about one half of a wave length.

Such flanges may be provided either solely along the extreme rows or along the extreme lines as in Fig. 2 or along both the extreme rows and the extreme lines, so

as to form in this latter case a continuous flange, as shown in Fig. 1.

It will be remarked that the invention is independent of the manner in which the elementary aerials are fed from'the energy source. They may be fed in any known manner, for instance in such a way as to obtain equal intensities in all the elementary radiators or to obtain intensities the amplitudes of which vary from one elementary radiator to the adjacent one in accordance with a predetermined law, say in accordance with a Gaussian curve.

Thus, the invention provides aerials having the same characteristics as the conventional aerials of the type considered at a greatly reduced cost, since the number of radiating elements required is reduced substantially by a half.

What I claim is: V

l. A compound directional aerial comprising a network of elementary radiating elements located at the apices of a checkerwork of lines and rows, the distances 20 between the successive elements in each row and each line being equal to one wave length, and a reflector located in a plane parallel with the network at about one quarter of a wavelength from the latter, overlapping slightly the network and including a plane section and inturned flanges extending along their edges into registry with the network on the outside of at least one'pair of extreme series of elements arranged respectively in the extreme rows and in the extreme lines.

2. A compound directional aerial comprising a network of elementary radiating elements located at the apices of a checkerwork of lines and rows, the distances between the successive elements in each row and each line being equal to one wavelength, and a reflector located in a plane parallel with the network at about one quarter of a wavelength from the latter, overlapping slightly the-network and including a plane section and inturned flanges extending along their edges into registry with the network on the outside of at least one pair of extreme series of elements arranged respectively in the extreme rows and in the extreme lines, the depth of said flanges being substantially equal to one half wavelength.

References Cited in the file of this patent UNITED STATES PATENTS 1,738,522 Campbell Dec. 10, 1929 2,455,403 Brown Dec. 17, 1948 Freedman Dec. 16, 1952 

